Attack and sustain switching circuit for an electronic musical instrument

ABSTRACT

An attack switching circuit is composed of a transistor, a key switch connected in the emitter circuit of the transistor, the transistor being connected with an input signal source and so biased as to be rendered into a nonconducting state when the key switch is left in an opened state, a coil of an electromagnet connected in series with the key switch and included in the emitter circuit, a capacitor also included in the emitter circuit in parallel with the key switch and coil and charged beforehand while the key switch is opened and discharged through the key switch and coil when the key switch is closed, and a magnetosensitive element disposed in the magnetic field of the electromagnet and connected through a high resistance to the collector of the transistor or to the input signal source, whereby an output of &#39;&#39;&#39;&#39;sustain&#39;&#39;&#39;&#39; is delivered from the collector circuit of the transistor and an output of &#39;&#39;&#39;&#39;attack&#39;&#39;&#39;&#39; characteristic is delivered from a junction point between the magnetosensitive element and the high resistance.

United States Patent [72] Inventor YasujiUchiyama Hamakita-shi, Japan [21] Appl. No. 811,788 [22] Filed Apr. 1,1969 [45] Patented Mar. 16, 1971 Nippon Gakki Seizo Kabushiki Kaisha, Nakazawa-Cho, Hamamatsu-shi, Shizuoka- [73] Assignee ken, Japan [32] Priority Apr. 2, 1968 J p [3 l 21 197/68 [54] ATTACK AND SUSTAIN SWITCHING CIRCUIT FOR AN ELECTRONIC MUSICAL INSTRUMENT Primary Examiner-Milton O. Hirshfield Assistant Examiner-U. Weldon Attorneyl-lolman, Glascock, Downing & Seebold ABSTRACT: An attack switching circuit is composed of a transistor, a key switch connected in the emitter circuit of the transistor, the transistor being connected with an input signal source and so biased as to be rendered into a nonconducting state when the key switch is left in an opened state, a coil of an electromagnet connected in series with the key switch and included in the emitter circuit, a capacitor also included in the emitter circuit in parallel with the key switch and coil and charged beforehand while the key switch is opened and discharged through the key switch and coil when the key switch is closed, and a magnetosensitive element disposed in the magnetic field of the electromagnet and connected through a high resistance to the collector of the transistor or to the input signal source, whereby an output of sustain is delivered from the collector circuit of the transistor and an output of attack characteristic is delivered from a junction point between the magnetosensitive element and the high resistance.

Patented March 16, 1971 3,571,482

Fl G. l

PRIORART FIG. 3(a) FIG. 3(b) v F|G,3(C) INVENTOR YHSUJ'I' CHIYM R mm, M,

ATTORNEYS if-TACK AND SUSTAIN SWITCHING CIRCUIT FOR AN ELECTRONIC MUSICAL INSTRUMENT BACKGROUND OF THE INVENTION This invention generally relates to the field of a switching circuit to be employed in an electronic musical instrument, and more particularly to a switching circuit which is allowed to generate a sharp rising and falling tone as well as moderately rising and falling tone.

lI-leretofore, a tone which rises and falls moderately has been obtained from a sustain switching circuit, which, upon depression and release of a key switch, passes and interrupts a tone signal, in the form of voltage, in such a manner that the rising and falling features of an envelope of the tone signal is substantially moderate. Such a tone signal in the form of voltage and having an envelope rising and falling moderately is hereinafter called a sustain signal.

On the other hand, a tone rising and falling sharply was obtained by an attack switching circuit which allows to pass or interrupt a tone signal, in the form of voltage, in such a manner that the rising and falling features of the envelope of the tone signal thus obtained are substantially sharp (such a signal is hereinafter called an attack signal).

A typical example of the sustain" switching circuit widely used heretofore is illustrated in FIG. lof the accompanying drawing (described hereinafter). This circuit includes: bias resistors R1, R2; a load resistor R3; an emitter resistor R4; a sustain time-constant resistor R5; a rising time-constant resistor R6; a transistor TR; and a time-constant determining capacitor C.

In the operation, it is assumed that a-tone signal has been applied to an input terminal In of the switching circuit. Under such a condition, when a key switch SW is closed, the capacitor C which has been charged through a resistor R5 starts to discharge, and the emitter potential of the transistor TR is lowered. As a result, the transistor TR starts to conduct gradually, and the signal voltage at the output terminal T rises in accordance with a time-constant (in an ordinary case, about 10 ms.) determined by the capacitor C and a resistor R6. After a certain time period determined by the time-constant, the signal voltage obtained from the transistor TR settles to a constant value.

When the key switch SW is opened, a charging current is caused to flow into the capacitor C through the resistor R5 from a power source E2 which furnishes a sustain voltage, and the potential of the emitter of the transistor TR is gradually increased, thus shifting the transistor TR into a noncongluctive state. This in turn lowers the output signal from the output terminal T gradually after the switch SW is closed (in an ordinary case, this lowering period is about 2 ms.), and a sustain" signal voltage as described before can be obtained.

An attack" switching circuit of the conventional construction has been a complicated one, and, although it is not described herein, to consolidate the attack" switching circuit into the sustain switching circuit as shown in FIG. I for operation in unison was difficult. For this reason, the attack switching circuits had to be provided separately from the sustain switching circuits in the conventional electronic musical instruments, and this resulted in excessive complication and excessively high cost in the conventional instruments.

SUMMARY OF THE INVENTION 7 Therefore, the primary object of the present invention is to provide a novel construction of the switching circuit, whereby all of the above-described disadvantages are eliminated.

Another object of this invention is to provide a composite switching circuit operable by means of a key switch, whereby the sustain signal and the attack signal can be obtained from the respective output terminals of the composite switching circuit.

Still another object of this invention is to provide a novel construction of a composite switching circuit wherein an electromagnet and a magnetosensitive element located in the neighborhood of the electromagnet are provided, whereby the attack" and the sustain signals can be created from a single switching circuit.

These and other objects of the invention can be achieved by providing a novel construction of a composite switching circuit which comprises: a transistor having a tone signal source connected at the input terminal connected to the base thereof, and is biased into an inoperative condition when a key switch inserted in the emitter circuit thereof is opened; an electromagnet connected in series with the key switch inserted in the emitter circuit of the transistor; a capacitor charged from a power source to a predetermined potential at the time the key switch is opened, and causes a discharge current to flow through the key switch and a coil of the electromagnet when the key switch is closed; and a magnetically sensitive element connected across the collector and the ground or across the tone signal source and the ground, whereby, with closing and opening of the key switch, a sustain output is obtained from the collector of the transistor and an attack output is obtained from the junction point between the magnetically sensitive element and a high resistor.

The invention will be better understood from the following detailed description with respect to a preferred embodiment thereof when read together with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the drawing FIG. 1 is a circuit diagram showing an example of the conventional switching circuit;

FIG. 2 is a circuit diagram showing an example of an attack switching circuit according to the present invention; and

FIGS. 3a, 3b, 3c are waveform diagrams respectively showing waveforms of two output voltages and one current flowing through a coil of the circuit shown in FIG. 2.

DETAILED DESCRIPTION Referring now to FIG. 2 which illustrates an attack switching circuit according to the present invention, and also to FIG. 3 showing waveforms of output voltages and a coil current, it is apparent that the attack switching circuit is comprised of: bias resistors R7 and R8, a load resistor R9, an emitter resistor R10, a resistor R11 for determining a timeconstant for the sustain" signal, a capacitor C for determining the same time-constant, a magnetosensitive element 1, a magnet 2 which imparts a magnetic field to the magnetosensitive element 1, an electromagnet 3 having a coil 4 and a core 5, another magnetosensitive element 6 inserted in the airgap portion of the electromagnet 3, and a resistor R12 electrically isolating the output terminal Tl from the output terminal T2.

On an input terminal T0 of the switching circuit, a tone signal source is connected, and a tone signal therefrom is applied to the input terminal To. On terminals T3 and T4, it is assumed that for instance, +l 2V and +3V are applied. The magnetosensitive element 1 and a magnet 2 in cooperation act as a switch comparable to the above-described key switch SW.

At the condition illustrated in FIG. 2, the key switch SW is not yet depressed, that is, the magnetosensitive element I is under the influence of a strong magnetic field of the magnet 2, and the resistance of the magnetosensitive element I is high. In this case, the capacitor C is charged from the terminal T4 (or for instance +3V) through a resistor R11.

When the key switch SW is depressed, that is, the magnet 2 is shifted to a remote position, and the resistance of the magnetosensitive element It is lowered, the capacitor C is discharged throughthe magnetosensitive element l and a coil 4 of the electromagnet c 3, and the emitter voltage of the transistor TR is lowered thereby causing the transistor TR to be conductive. Since the magnetosensitive element I and the magnet 2 operate in the same manner as the key switch SW, the combination of the element l and the magnet 2 is also called a key switch in the following description.

With discharging of the capacitor C, the potential of the capacitor C equivalent to that of the junction point between the capacitor C and the resistor R is gradually lowered, and the output signal voltage at the terminal T1 is raised as shown in FlG. 3a from the instant when the key switch is depressed.

When the key switch is thereafter released, the magnet 2 is brought back to the original position confronting the magnetosensitive element 1, and most of the magnetic flux is applied to the magnetosensitive element 1 to increase the resistance value of the element 1. Accordingly, a charging current starts to flow from the terminal T4 to the capacitor C through the resistor R11, and the potential of the junction point between the resistor R10 and the capacitor C is gradually increased until, finally, the transistor is brought into a nonconductive state. Thus, the output signal voltage at the terminal T1 is gradually lowered after the instant when the key switch is released, and a so-called sustain signal is obtained from the terminal T1.

On the other hand, the discharge current of the capacitor C through the coil 4 of the electromagnet 3 is at its maximum value at the instant the key switch is depressed as indicated in FIG. 30, and the magnetic field created by the current flowing in the coil 4 has the same characteristic. This magnetic field is applied to the magnetosensitive element 6, and the resistance value of the element 6 is also varied depending on the variation of the magnetic field. As a result, the signal current flowing from the terminal T1 through the resistor R12 to the mag netosensitive element 6 is also varied and an output signal voltage obtained from the output terminal T2 will be as shown in FIG. 3b. This means that a signal representing a tone signal of highly attacking effect can be obtained from the output terminal T2. Interference between the terminals T1 and T2 is prevented by the provision of the high resistance R12 therebetween.

ln the circuit shown in FIG. 2, since one terminal of the resistor R12 is connected to the terminal Tl, there is attained an advantageous effect of allowing the attack signal to be interrupted completely by the same switching element 6 for the sustain signal even if the resistance ratio thereof at the time of closing-and-opening conditions is not sufficiently large. In other words, the magnetosensitive element may be of moderate variation range depending on the variation in the magnetic field, thus enabling the use of a cheaper element.

Otherwise, a terminal of the resistor R12 may also be connected to the input terminal To, connected to the input tone signal source, instead of the above-described output terminal Tl, via a switch S and if the resistance ratio of the magnetosensitive element 6 connected therein is selected to be a sufficiently high value, the rising characteristic of the attack" signal is not influenced by the sustain" signal but is caused to be proportional to the current variation in the electromagnet 3, whereby the attack signal of sharp rising and falling nature can be obtained.

Since the switching circuit according to the present invention is as described above, a sustain" signal as well as attack signal can be obtained simultaneously when the tone signal from the tone source is open-and-closed. Furthermore, because substantially no contact point is employed in the switching circuit, the possibility of trouble can be substantially eliminated, and advantageous features such as minimizing the size of the musical instruments and lowering the price thereof can be achieved.

lclaim:

1. An attack switching circuit to be employed in an electronic musical instrument for obtaining attack signals and sustain signals simultaneously, said switching circuit comprising: a transistor the input circuit of which is connected with a tone signal source, said transistor being further biased so that it is brought into a nonconductive state at the time the switching device is opened; a switching device connected in the emitter circuit of said transistor; an electromagnet also connected in the emitter circuit of said transistor; an electromagnet also connected in the emitter circuit of said transistor in senes wlth said switching device; a capacitor also connected in the emitter circuit in parallel with said switching device and said electromagnet, said capacitor being charged when said switching device is opened and discharged through said electromagnet and said switching device when the switching device is closed; and a magnetosensitive element located near said electromagnet and connected through a high resistance across the collector circuit and the ground, whereby the sustain signals are obtained from the collector of the transistor and attack" signals are obtained simultaneously from the junction between the magnetosensitive element and the high resistance.

2. An attack switching circuit as defined in claim 1 wherein said switching device is a key switch of mechanical operation.

3. An attack switching circuit as defined in claim 1 wherein said switching device is a combination of a magnet and a magnetosensitive element the resistance of which is varied by the relative position of said two elements.

4. An attack switching circuit as defined in claim l, wherein said magnetosensitive element located near said electromagnet is connected through a high resistance across the tone signal source and the ground. 

1. An ''''attack'''' switching circuit to be employed in an electronic musical instrument for obtaining ''''attack'''' signals and ''''sustain'''' signals simultaneously, said switching circuit comprising: a transistor the input circuit of which is connected with a tone signal source, said transistor being further biased so that it is brought into a nonconductive state at the time the switching device is opened; a switching device connected in the emitter circuit of said transistor; an electromagnet also connected in the emitter circuit of said transistor; an electromagnet also connected in the emitter circuit of said transistor in series with said switching device; a capacitor also connected in the emitter circuit in parallel with said switching device and said electromagnet, said capacitor being charged when said switching device is opened and discharged through said electromagnet and said switching device when the switching device is closed; and a magnetosensitive element located near said electromagnet and connected through a high resistance across the collector circuit and the ground, whereby the ''''sustain'''' signals are obtained from the collector of the transistor and ''''attack'''' signals are obtained simultaneously from the junction between the magnetosensitive element and the high resistance.
 2. An ''''attack'''' switching circuit as defined in claim 1 wherein said switching device is a key switch of mechanical operation.
 3. An ''''attack'''' switching circuit as defined in claim 1 wherein said switching device is a combination of a magnet and a magnetosensitive element the resistance of which is varied by the relative position of said two elements.
 4. An ''''attack'''' switching circuit as defined in claim 1, wherein said magnetosensitive element located near said electromagnet is connected through a high resistance across the tone signal source and the ground. 